The present invention relates to a composition (preferably low pH composition of pH less than 7.5, more preferably less than 7.3, more preferably less than 7.1) which comprises both insoluble surfactant (e.g., insoluble soaps and insoluble synthetic, non-soap surfactants); and soluble surfactant (e.g., principally soluble synthetic, although the bar may comprise less than 1% soluble soap), yet have a squeaky, non-slimy rinse.
Generally, mild bars comprise synthetic surfactants, wherein the synthetic is used to alleviate harshness of pure soap or predominantly soap bar.
Although soap is harsh, it is also desirable to many consumers because the soap creates a feeling on the skin during rinse which has been described as “squeaky”. This squeaky feeling drives a perception of cleanliness and, as noted, is desirable among soap consumers.
In an effort to maintain the mildness associated with synthetic surfactants, while at the same time providing the squeaky sensorial feel desirable to many consumers, applicants have noted that use of a soluble surfactant system (in addition to insoluble surfactant present), wherein at least a certain percentage of the total soluble system is calcium sensitive, results in bars which are both mild and perceptibly “squeaky”.
Although there is not necessarily a direct correlation between low soluble surfactant and pH (i.e., other components in the bar composition also affect pH values), by minimizing or eliminating the use of soluble soap (i.e., so there is less than 1.0% by wt., preferably less than 0.5% by wt. total bar of soluble soaps), this helps to maintain pH of the bar composition lower so that it will have a pH of less than 7.5, preferably less than 7.3.
Stated differently, and without wishing to be bound by theory, when there is more available soluble soap, this soap will solubilize on dilution and can cause a higher pH. Insoluble soap, on the other hand, does not solubilize and is not available to raise pH. Thus, while as noted there are other compounds available which can raise pH in solution, minimizing or eliminating soluble soap altogether is an effective way to keep pH lower.
The surfactants and/or soap which are present and are not soluble in water (surfactant or soap of less than 1% solubility) will also not be calcium sensitive since they do not dissolve in water where the calcium ions will be available to interact.
In copending application, U.S. Ser. No. 10/883,326 to Morikis et al., entitled “Mild Synthetic Detergent Toilet Bar Composition”, filed Jul. 1, 2004, applicants also seek to deliver squeaky sensation in a mild surfactant system. That application however uses 2% to 25% by wt. soluble soap (which has a tendency to raise pH); and uses ratios of components rather than predominantly calcium precipitated synthetic to provide the desired squeaky feel. Although pH may be lowered in other ways, Morikis et al. does not recognize the criticality of lower pH (i.e., pH below 7.5, preferably below 7.3, more preferably below 7.1) and typically has compositions with pH above 7.5.
Another co-pending U.S. application to Farrell et al., U.S. Ser. No. 10/756,615, filed Jan. 13, 2004, does not recognize that specific non-soap synthetic (i.e., those which are calcium sensitive and which precipitate under given hardness conditions) must be present in order to obtain the desired squeaky, non-slimy effect. The subject application is thus a clear selection over the disclosure of Farrell et al.